1. Field of the Disclosure
Embodiments disclosed herein generally relate to methods and assemblies that include a ball valve used to start and stop fluid flow. More specifically, embodiments disclosed herein relate to a valve assembly that uses a ball valve to seal against fluid flow from both the upstream and downstream directions.
2. Background Art
The use of ball valves to start and stop the flow of fluids is well known in the art. Ball valves typically include a valve ball that is located between two seats in the middle of a passage. The valve ball has a through hole, and can be rotated between two positions. U.S. Pat. No. 5,246,203, issued to McKnight et al. (“McKnight”), incorporated by reference in its entirety, discloses an oilfield valve that incorporates a ball valve mechanism. The mechanics of a typical ball valve mechanism are demonstrated in the McKnight patent.
In a first position, as demonstrated in FIG. 1A, the through hole of the valve ball will align with the passage of the pipe or drill string. This position will generally allow complete and undisrupted fluid flow through the passage. The valve ball may then be rotated from this position into a second position, as demonstrated in FIG. 1B, to be misaligned with the passage of the pipe, thereby disrupting fluid flow. Each of the seats surrounding the valve ball, one upper seat and one lower seat, seal against the valve ball, not allowing flow between the valve ball and the seat. Thus, the valve ball, coupled with the two seats sealing against the valve ball, may stop fluid flow through the pipe passage when the valve ball is positioned in the closed position to misalign with the through hole passage by having the seats seal up against the valve ball. In FIG. 1B, a seal is made between the seats, 101 and 102, and the valve ball 105 to completely prohibit flow through the passage. The valve ball has the ability to seal against the seats to be effective against even the highest of pressures, allowing the arrangement to be used as a ball valve.
One issue with this type of ball valve arrangement is that when the valve ball 105 is in the second position, blocking flow through the passage, as seen in FIG. 1B, the valve ball 105 may not be able to effectively seal against the fluid flow, such as both in the upstream and downstream direction. For example, debris comes between the valve ball 105 and the seat 102, only sealing on the downstream seat 101 may be achieved. In such an example, if a fluid force is applied from the downstream direction, the debris may cause the valve to be unable to effectively seal between the valve ball 105 and the seat 102, thereby resulting in a leakage through the ball valve arrangement.
U.S. Pat. No. 4,890,643, issued to Oliver (“Oliver”), incorporated by reference in its entirety, discloses a bi-directional sealing valve that incorporates ball valve mechanisms. As such, an embodiment disclosed by Oliver is shown in FIG. 2, in which a bi-directional sealing valve 200 includes a first valve ball (upstream valve ball) 205A and a second valve ball (downstream valve ball) 205B. The first valve ball 205A seals against an upper seat 210, the second valve ball 205B seals against a lower seat 220, and both the first valve ball 205A and the second valve ball 205B seal against a middle seat 215 disposed between the first valve ball 205A and the second valve ball 205B. The upper seat 210 is supported by a first spring (upstream spring) 221A, and the lower seat 220 is supported by a second spring (downstream spring) 221B.
When a fluid force is applied from above using the bi-directional sealing valve 200, such as having a downstream fluid force applied thereto, the first valve ball 205A and the second valve ball 205B may be used in combination to inhibit fluid flow through the sealing valve 200. Particularly, when in closed positions, the first valve ball 205A may contact and seal against the middle seat 215, and, if necessary, the second valve ball 205B may translate the fluid force to the lower seat 220 to compress the spring 221B. During compression of the spring 221B, the second valve ball 205B “floats” down to stay in sealing contact with the lower seat 220. Because the middle seat 215 is firmly positioned within the sealing valve 200, the middle seat 215 does not move with second valve ball 205B. The space between the middle seat 215 and the second valve ball 205B provides an opening for the fluid to travel through, in which the fluid then fills up the valve ball 205B. This fluid flow then translates the fluid force to the lower end of the second valve ball 205B into the lower seat 220. This translation of the fluid force is shown in FIG. 1B. As the fluid enters the valve ball 105, the resultant fluid force moves from location 151, on the outer diameter on top of the valve ball 105, to location 152, on the inner diameter inside of the valve ball 105.
In a similar fashion, when a fluid force is applied from below using the bi-directional sealing valve 200, such as having an upstream fluid force applied thereto, the second valve ball 205B may contact and seal against the middle seat 215, and, if necessary, the first valve ball 205A may translate the fluid force to the upper seat 210 to compress the spring 221A.
The sealing valve of Oliver discloses an arrangement that has two valve balls, in which each of the valve balls may be able to float in one of either the upstream direction or the downstream direction, thereby enabling each of the valve balls to seal in one of either the upstream direction or the downstream direction. This structure and arrangement may increase the reliability of the sealing valve in Oliver, as each valve ball only has the responsibility to effectively seal in only one direction (either the upstream direction or the downstream direction).
However, this arrangement in Oliver requires the use of multiple valve balls, thereby increasing the number of components necessary for the sealing valve to be effective. As such, this arrangement may increase the overall cost of the sealing valve, as more components within the valve may be more expensive, may decrease the overall reliability of the sealing valve, as more components within the valve may lead to more surfaces that must correctly seal against fluid flow, and may decrease the overall compatibility and use of the sealing valve, as more components within the valve may change the usual dimensions and increase the overall size of the valve. Accordingly, there exists a need to provide a ball valve assembly that may minimize the overall size and number of components necessary to operate the valve while still being capable of sealing against the flow of fluid, both upstream and downstream.